Hybrid optical-digital pattern recognition apparatus and method

Abstract

An improved apparatus and method of pattern recognition and of providing pattern recognition data, which possesses the advantages of optical power spectral analysis and digital image processing. An optical read-only memory means such as a photographic transparency is sampled at a plurality of sampling locations with a beam of coherent light. After passage through the transparency, the beam is directed either to a first channel including a transform lens and a wedge-ring detector or to a second channel including an imaging lens and a photodetector array. The improved pattern recognition data is the spatial frequency data provided by the wedge-ring detector and the spatial intensity data provided by the array detector. Hierarchal pattern recognition decisions are made using the two types of data during processing operations to provide improved pattern recognition results.

We claim: 
     
       1. An apparatus for providing improved pattern recognition data, comprising, optical read-only memory means for storing a two dimensional image function having patterns to be recognized,   coherent light source means for irradiating said read-only memory means with coherent light, which becomes modulated with information corresponding to said two dimensional image function.   means responsive to said information contained in said coherent light for providing first data indicative of the optical power spectrum of said two dimensional image function, and   means also responsive to said information contained in said coherent light for providing second data indicative of the spatial intensity distribution of said two dimensional image function,   said improved pattern recognition data comprising said first and second data.   
     
     
       2. The apparatus of claim 1, wherein said means for providing first data indicative of the optical power spectrum of said image function includes optical means for providing the Fourier transform of said image function or of portions thereof. 
     
     
       3. The apparatus of claim 2, wherein said optical means comprises a transform lens means. 
     
     
       4. The apparatus of claim 3, wherein said means for providing second data indicative of the spatial intensity distribution of said image function includes photodetector array means. 
     
     
       5. The apparatus of claim 4, wherein said coherent light source means provides a sampling beam for irradiating said read-only memory means which is substantially smaller in diameter than the surface area of said memory means, further including translation means for moving said read-only memory means so that said beam irradiates it at a plurality of sampling locations. 
     
     
       6. The apparatus of claim 5, wherein said read-only memory means is a photographic transparency and said beam of light passes through said transparency. 
     
     
       7. The apparatus of claim 6 further defining two optical channels, a first of which includes said transform lens means and wedge-ring detecting means, and a second of which includes an imaging lens means and said photodetector array means. 
     
     
       8. The apparatus of claim 7 further including optical beam deflection means for directing said coherent light beam after passage through said transparency either to said first channel or said second channel. 
     
     
       9. An improved pattern recognition method comprising the steps of, providing a photographic transparency which stores a two dimensional image function having patterns to be classified,   providing a beam of coherent light,   sampling said transparency at a plurality of sampling locations with said beam of light, whereby after passing through said transparency said beam of light is modulated with information corresponding to a portion of said two dimensional image function,   deriving first data which is indicative of the optical power spectrum of said sampled locations of said image function from said information in said beams of light,   deriving second data which is indicative to the spatial intensity distribution of said sampled locations of said image function from the information contained in said beams of light,   analyzing said first data indicative of said optical power spectrum to determine whether it meets predetermined criteria, and,   if said first data meets said predetermined criteria, analyzing said second data.